[RFC PATCH v12 14/26] mm/rmap: recognize read-only tlb entries during batched tlb flush

[Byungchul Park <byungchul@sk.com>]

Functionally, no change.  This is a preparation for luf mechanism that
requires to recognize read-only tlb entries and handle them in a
different way.  The newly introduced API in this patch, fold_ubc(), will
be used by luf mechanism.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 include/linux/sched.h |  1 +
 mm/rmap.c             | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index c4ff83e1d5953..a217d6011fdfe 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1381,6 +1381,7 @@ struct task_struct {
 
 	struct tlbflush_unmap_batch	tlb_ubc;
 	struct tlbflush_unmap_batch	tlb_ubc_takeoff;
+	struct tlbflush_unmap_batch	tlb_ubc_ro;
 
 	/* Cache last used pipe for splice(): */
 	struct pipe_inode_info		*splice_pipe;
diff --git a/mm/rmap.c b/mm/rmap.c
index 1581b1a00f974..3ed6234dd777e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -775,6 +775,7 @@ void fold_luf_batch(struct luf_batch *dst, struct luf_batch *src)
 void try_to_unmap_flush_takeoff(void)
 {
 	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+	struct tlbflush_unmap_batch *tlb_ubc_ro = &current->tlb_ubc_ro;
 	struct tlbflush_unmap_batch *tlb_ubc_takeoff = &current->tlb_ubc_takeoff;
 
 	if (!tlb_ubc_takeoff->flush_required)
@@ -789,6 +790,9 @@ void try_to_unmap_flush_takeoff(void)
 	if (arch_tlbbatch_done(&tlb_ubc->arch, &tlb_ubc_takeoff->arch))
 		reset_batch(tlb_ubc);
 
+	if (arch_tlbbatch_done(&tlb_ubc_ro->arch, &tlb_ubc_takeoff->arch))
+		reset_batch(tlb_ubc_ro);
+
 	reset_batch(tlb_ubc_takeoff);
 }
 
@@ -801,7 +805,9 @@ void try_to_unmap_flush_takeoff(void)
 void try_to_unmap_flush(void)
 {
 	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+	struct tlbflush_unmap_batch *tlb_ubc_ro = &current->tlb_ubc_ro;
 
+	fold_batch(tlb_ubc, tlb_ubc_ro, true);
 	if (!tlb_ubc->flush_required)
 		return;
 
@@ -813,8 +819,9 @@ void try_to_unmap_flush(void)
 void try_to_unmap_flush_dirty(void)
 {
 	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+	struct tlbflush_unmap_batch *tlb_ubc_ro = &current->tlb_ubc_ro;
 
-	if (tlb_ubc->writable)
+	if (tlb_ubc->writable || tlb_ubc_ro->writable)
 		try_to_unmap_flush();
 }
 
@@ -831,13 +838,18 @@ void try_to_unmap_flush_dirty(void)
 static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
 				      unsigned long uaddr)
 {
-	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
+	struct tlbflush_unmap_batch *tlb_ubc;
 	int batch;
 	bool writable = pte_dirty(pteval);
 
 	if (!pte_accessible(mm, pteval))
 		return;
 
+	if (pte_write(pteval))
+		tlb_ubc = &current->tlb_ubc;
+	else
+		tlb_ubc = &current->tlb_ubc_ro;
+
 	arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, uaddr);
 	tlb_ubc->flush_required = true;
 
-- 
2.17.1